What is the most effective technique for modeling?
To define what is the most effective 3d modeling technic, all the know technics should be evaluated in several factors, such as:

Time demanded
Computational cost
Quality
Practicality

And be considered for all different artists, computer configurations, type of scenarios, and even consider if the technic can be incorporated in a production pipeline among other artists. So, it is impossible to answer your question accurately.
BUT
To help you discover more about the various techniques (or styles) to do a 3D model in a DCC software such as Blender. I would suggest you watch this video from Gleb Alexandrov as a good start.

Is there a more effective way to create more complex models or do I just need to practice more?

Also, as referred to in other comments, the modeling technic depends on what you are modeling, so maybe there is a better way to modeling, maybe not. But it is very common that along the process you discover ways to speed up or improve your knowledge to do 3D models.
And about practice, I guess the only person who can answer that is your employer or your clients. Because even if you have been modeling for 10 years, there are always new technics that you actually never practice. So it depends a lot on your expectations and demands.
Do your best, enjoy the process and stay curious.